1. Field of the Invention
The present invention relates to a light source device, a display device and a television receiver, and more specifically relates to a light source device for a display device or for a television receiver such that luminance and/or a color tone of light sources can be corrected, a display device having the light source device, and a television receiver having the display device.
2. Description of the Related Art
A display device having a non-self-emissive display panel such as a translucent liquid crystal panel sometimes includes a light source device placed behind the liquid crystal display panel or on a lateral side of the liquid crystal display panel. This type of display device is arranged so that light emitted from the light source device passes through the display panel from behind to its front side, and makes an image displayed visible on the front side of the display panel.
As light sources incorporated in such a light source device, fluorescent tubes such as hot cathode tubes and cold cathode tubes are widely used, and nowadays light-emitting diodes (LEDs) are also used.
FIG. 13 is an exploded perspective view schematically illustrating the structure of a conventional light source device in which light-emitting diodes are used as light sources. In a light source device 9 in FIG. 13, light source blocks 91 each having the shape of a plate are placed on a front surface of a chassis 92. Each of the light source blocks 91 contains light-emitting diodes 93 each of which includes a red-color light-emitting diode, a green-color light-emitting diode and a blue-color light-emitting diode. The light source blocks 91 are capable of emitting white light by mixing red light, green light and blue light which are emitted respectively from the red-color, green-color and blue-color light-emitting diodes.
Incidentally, light-emitting diodes sometimes have individual differences in properties such as luminance and a color tone. Therefore, the red-color, green-color and blue-color light-emitting diodes included in the light-emitting diodes are placed at the time of manufacture of the light source device so that the luminance and/or the color tone become uniform within each of the light source blocks. However, the luminance and/or the color tone sometimes differ from one light source block to another light source block. In some cases, the luminance and/or the color tone gradually have differences due to change over time in properties of the light-emitting diodes even though they do not differ from one light source block to another light source block at the time of manufacture or shipment of the light source device. Those differences in the luminance and/or the color tone among the light source blocks in the light source device cause irregular luminance and/or irregular color, which could worsen the display quality of the light source device or the display device incorporating the light source device.
In order to prevent the irregular luminance and/or the irregular color caused by the differences in the properties of the light-emitting diodes, various proposals have been made such as inclusion of a mechanism for correcting the luminance and/or the color tone in accordance with the differences in the properties of the light-emitting diodes in the light source device or the display device.
As a prior art literature relating to the present invention, Japanese Patent Application Unexamined Publications Nos. 2003-274646 and Hei 09-197373 are cited. As a manner of adjusting display colors and brightness on a screen of a display device including LEDs as light sources, a technique disclosed in Japanese Patent Application Unexamined Publication No. 2004-184852 is cited. However, a manner of improving uniformity within the screen is not disclosed.
The correction of the luminance and/or the color tone among the light source blocks is made by making the color light-emitting diodes of each color emit light which are included in the light-emitting diodes contained in the light source block subjected to the correction, measuring the luminance of the color light-emitting diodes of each color, and calculating correction amounts of the luminance of the color light-emitting diodes of each color. Accordingly, the measurement needs to be performed the number of times which is computed by multiplying the number of the light source blocks by the number of the colors of the color light-emitting diodes included in one light-emitting diode, which increases the total time required for the measurement of the luminance. Especially, accompanied by recent increases in the size of a liquid crystal display panel, the number of the light source blocks incorporated in the light source device goes up, which further increases the total time required for the measurement of the luminance.
In order to make the correction of the luminance and/or the color tone with accuracy, it is preferable to perform the measurement of the luminance in a state similar to an actual usage state of the display device or the light source device. However, the display device cannot make regular display during the measurement of the luminance of the color light-emitting diodes. This is because if the measurement of the luminance is performed during the use of the display device, a user could feel strangeness with an image displayed on the display panel. Meanwhile, if it is arranged that a user performs the operation for the correction of the luminance and/or the color tone among the light source blocks, the user could feel inconvenience in using the display device.